PURIFICATION AND CHARACTERIZATION OF 6-CHLOROHYDROXYQUINOL 1,2-DIOXYGENASE FROM STREPTOMYCES-ROCHEI-303 - COMPARISON WITH AN ANALOGOUS ENZYME FROM AZOTOBACTER SP STRAIN-GP1

The enzyme which cleaves the benzene ring of 6-chlorohydroxyquinol was purified to apparent homogeneity from an extract of 2,4,6-trichloroph enol-grown cells of Streptomyces rochei 303. Like the analogous enzyme from Azotobacter. sp. strain GP1, it exhibited a highly restricted su bstrate specificity and was able to cleave only 6-chlorohydroxyquinol and hydroxyquinol and not catechol, chlorinated catechols, or pyrogall ol, Nb extradiol-cleaving activity was observed, In contrast to 6-chlo rohydroxyquinol 1,2-dioxygenase from Azotobacter sp, strain GP1, the S , rochei enzyme had a distinct preference for 6-chlorohydroxyquinol ov er hydroxyquinol (k(cat)/K-m 1.2 = 0.57 s(-1) mu M(-1), respectively). The enzyme from S, rochei appears to be a dimer of two identical 31-k Da subunits. It is a colored protein and was found to contain 1 mol of iron per mol of enzyme. The NH2-terminal amino acid sequences of 6-ch lorohydroxyquinol 1,2-dioxygenase from S, rochei 303 and from Azotobac ter sp. strain GP1 showed a high degree of similarity.